Synthetic studies on callipeltin A: stereoselective synthesis of (2R,3R,4S)-3-hydroxy-2,4,6- trimethylheptanoic acid

An efficient and highly stereocontrolled synthesis of protected (2R,3R,4S)-3-hydroxy-2,4,6-trimethylheptanoic acid, the beta-hydroxy acid unit that acylates the N-terminus of callipeltin A, has been devised starting from methyl (2S)-2-methyl-3-hydroxypropionate. Comparison of NMR data with the corresponding fragment obtained from the acid hydrolysate of callipeltin A indicates that the stereostructure of the above fragment should be revised